A three coordinate measuring machine is a measuring system which measures three dimensional coordinates of surface points on a workpiece through relative movement between a probe system and the workpiece. An object to be measured is located in the measuring space of the three coordinate measuring machine, and position coordinates of measuring points on the object to be measured are obtained by a contact or non-contact detection system. Deviations between real contour values and theoretical contour values of the object to be measured are derived by mathematical comparison of spatial coordinate values of these points using a software, so the object can be determined as whether it meets precision requirements. Vehicle components and parts have characteristics like high quality requirement, large amount and variance in shape, so an ideal solution for conducting geometrical measurement and quality control of various vehicle components and parts is using a three coordinate measuring machine. For example, for various single pieces of sheet metal, welded pieces, assemblies or other vehicle components and parts, a particular vehicle component or part shall be fixedly located on a clamp, and the clamp in turn is located relative to a platform of the measuring machine, so the vehicle component or part in measuring machine can be measured to determine the spatial position of it. For the reason that the vehicle components and parts to be measured are generally relatively big and heavy, the clamp has also a relative large size and weight to meet the requirement on supporting strength. A conventional clamp for three coordinate measuring generally comprises a support assembly and locating-clamping devices. The locating-clamping devices are configured for clamping and locating a component or part to be measured. The locating-clamping devices are fixedly supported by the support assembly, and the support assembly is formed by a process which involves welding pieces of carbon steel or assembling profiles of aluminum alloy. The support assembly has a rectangular frame structure, or is formed by fixing several vertical supporting plates onto a base plate. This type of conventional clamp for measuring is very bulky, which results in inconvenience in transportation, waste in material in manufacturing and low reusage rate. In the condition that profiles of aluminum alloy are used, although the weight can be lowered down, the rectangular frame is still relative bulky. In addition, the effect of temperature on dimensions should be considered in manufacturing since coefficient of linear expansion of profiles of aluminum alloy is high.